Passive translational velocity measurement from optical information

A system for determining a linear speed (Δv) of an object, comprising:

• a) a set of photoreceptors disposed on the object, composed of subsets of 3 photoreceptors, said subset of photoreceptors (35i, o1, o2, o3) measuring light intensities I(t) and being arranged to cover identical angular apertures pointing in different azimuthal directions, each different azimuthal direction defines a detection length (λi;
• i=1, . . . , k) of a series of detection lengths (λ) as seen in a direction of the linear speed (Δv) to be determined;
• b) means (C) for calculation the linear speed (Δv) for evaluation subsets (36j;
• j=1, . . . , k−1), each evaluation subset (36j) comprising the intensity inputs of three adjacent photoreceptors (o1, o2, o3), by performing for at least part of the subsets (36j);
• c) subtracting the light intensities inputs from two extreme photoreceptors (o1, o3) of each evaluation subset (36j) to receive a first difference signal (s13);
• d) splitting the first difference signal (s13) on two lines, one line delaying the difference signal (s13) by a temporal delay (τ);
• e) subtracting the signals (s13, delayed s13) from the two lines to receive a second difference signal (ts13);
• and
• f) multiplying the second difference signal (ts13) with the input from a central photoreceptor (o2) to achieve an output signal (sso) being indicative for the linear speed (Δv).